WO2018041296A1

WO2018041296A1 - Sensor assembly for determining a number of rotations of a permanent magnet

Info

Publication number: WO2018041296A1
Application number: PCT/DE2017/100676
Authority: WO
Inventors: Jean-Francois Heyd; Wai-Wai Buchet
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2016-08-30
Filing date: 2017-08-10
Publication date: 2018-03-08
Also published as: CN109564106A; CN109564106B; US10739163B2; KR20190045180A; DE102016216326A1; DE112017004298A5; KR102462298B1; US20190234761A1

Abstract

The invention relates to a sensor assembly (2) for determining a number of rotations (36) of a permanent magnet (1). Each end surface (4, 5) of the permanent magnet lies on an X-Y plane (6), and a central axis (7) extends transversely to the X-Y plane and coaxially to a rotational axis (8) of the permanent magnet. The permanent magnet has an opening (13) coaxially to the central axis and precisely two poles (9, 10) which are arranged on opposite sides (11, 12) of the permanent magnet on the X-Y plane such that the permanent magnet is magnetized diametrically. An internal circumferential surface (14) and an external circumferential surface (15) each extends substantially parallel to the central axis. A first sensor (33) is arranged in a stationary manner relative to the permanent magnet, which can be rotated about the rotational axis, wherein the first sensor is arranged at a distance from the permanent magnet in an axial direction (34), i.e. parallel to the rotational axis, and at a distance (20) from the rotational axis in a radial direction (35) radially outside of the external circumferential surface. The distance is selected such that a vector sum of a radial flux density (21) and a tangential flux density (22) do not fall below a first threshold (23) and do not exceed a second threshold (24).

Description

Sensor arrangement for determining a number of revolutions of a

permanent magnets

The invention relates to a sensor arrangement for determining a number of revolutions of a permanent magnet. The permanent magnet is in particular arranged rotatable relative to a stationary first sensor. In particular, the sensor arrangement is provided for determining a number of revolutions of a drive unit of an actuator, preferably a clutch actuator. The clutch actuator is in particular for actuating a clutch, for. B. a friction clutch, a motor vehicle. The drive unit is in particular a rotor of an electric motor, which is connected in a rotationally fixed manner to the permanent magnet, so that the number of revolutions of the rotor can be determined. On the number of revolutions of the rotor is in particular a position of a displaceable in an axial direction, actuation unit of the actuator along the axial direction determinable.

In clutch actuators an accurate determination of the axial position of an actuator or the angular position z. B. a rotor necessary. In new constructions of such clutch actuators, it is now necessary to arrange the sensors used for this purpose at a distance from an axis of rotation. In this case, dynamic tolerances (ie occurring during operation of the clutch actuator deviations from a starting position) must be taken into account, for. B. an eccentricity of individual components and a changing air gap between the first sensor and a permanent magnet used.

Proceeding from this, the object of the present invention is to at least partially solve the problems known from the prior art. In particular, a particularly suitable sensor arrangement for determining a number of revolutions of a permanent magnet is to be proposed, wherein the number of revolutions of a drive unit of an actuator should be determinable over the number of revolutions of the permanent magnet. The object is solved by the features of the independent claim. Advantageous developments are the subject of the dependent claims. The features listed individually in the claims can be combined in a technologically meaningful manner and can be supplemented by explanatory facts from the description and details of the figures, with further embodiments of the invention are shown.

The invention relates to a sensor arrangement for determining a number of revolutions of a permanent magnet, wherein end faces of the permanent magnet each lie in an X-Y plane and a central axis extends transversely to the X-Y plane and coaxial with a rotation axis of the permanent magnet; wherein the permanent magnet has exactly two poles arranged in the X-Y plane on opposite sides of the permanent magnet so that the permanent magnet is diametrically magnetized; wherein the permanent magnet has an opening coaxial with the central axis; wherein an inner peripheral surface and an outer peripheral surface each extend substantially parallel to the central axis; wherein a, relative to the rotatable about the axis of rotation rotatable permanent magnet arranged first sensor in an axial direction, that is parallel to the axis of rotation, at a distance from the permanent magnet and in a radial direction radially outside the outer peripheral surface is arranged at a distance from the axis of rotation; wherein the distance is selected such that a vector sum of a radial flux density and a tangential flux density does not fall below a first limit value and does not exceed a second limit value.

In particular, the distance between the axis of rotation and a center of the first sensor along the radial direction is determined.

In particular, a magnetic field of the permanent magnet has a magnetic flux that can be represented at any position in the magnetic field by a vector; wherein the vector comprises a tangential magnetic field direction, a radial magnetic field direction and a normal magnetic field direction; wherein the tangential magnetic field direction is parallel to the XY plane and parallel to an orientation of the poles; in which the radial magnetic field direction is parallel to the XY plane and transverse to the orientation of the poles; wherein the normal magnetic field direction is transverse to the tangential magnetic field direction and the radial magnetic field direction; wherein the first sensor is a multi-turn sensor suitable for determining a number of revolutions of the permanent magnet, the first sensor for determining the number of revolutions detecting magnetic field directions of magnetic flux in the radial magnetic field direction and the tangential magnetic field direction.

In particular, the inner peripheral surface and / or the outer peripheral surface may have a different shape from a parallel extension to the central axis, z. B. a curvature or conicity or the like.

The permanent magnet in particular has a substantially hollow cylindrical shape and a central axis extending between two, in particular parallel to each other end faces along a rotation axis. The permanent magnet is diametrically magnetized, i. H. the two magnetic poles are each disposed on an outer circumferential surface, on opposite sides of the permanent magnet. The poles can be connected by a straight line that intersects the axis of rotation of the permanent magnet. The position of the magnetic field directions, the plane and the central axis are further explained in the figure description.

The opening arranged coaxially with the central axis extends from the first end side to the second end side. The inner peripheral surface formed by the opening extends parallel to the central axis and is in particular circular.

The outer peripheral surface is in particular circular.

In particular, the first limit is 12 mT [MilliTesla], preferably 15 mT, and the second limit is 37 mT, preferably 35 mT.

In particular, the distance is through Distance = k ^* diameter outer peripheral surface + R ₀ determined, where k and R ₀ are determined depending on at least the diameter of the outer peripheral surface and the distance.

The diameter of the outer peripheral surface is in particular an average diameter. That if deviations from a circular shape or from an outer peripheral surface parallel to the rotation axis are present, the average diameter, averaged by surface portions arranged at different diameters, can be used to determine the diameter of the outer circumferential surface.

In particular, the distance is determined between each other, along the axial direction, nearest points of the first sensor and permanent magnet.

In particular, at a distance between 3 and 6 mm [millimeter] and a diameter of the outer peripheral surface between 18 and 30 mm for k and R ₀ :

k = 0.36 and

Ro = 7.45.

In particular, the first sensor with a maximum deviation of 10% of the determined distance from the axis of rotation is to be arranged.

In particular, the permanent magnet between the end faces has a thickness of 3 to 6 mm.

The arrangement of the first sensor at a predetermined distance from the axis of rotation or to the outer peripheral surface of the permanent magnet surprisingly leads to a smaller difference between a minimum vector sum and a maximum vector sum of the magnetic flux density in the radial magnetic field direction and the tangential magnetic field direction, in particular over the service life of the permanent magnet and taking into account the case of use occurring tolerances. Furthermore, a smaller spread of the vector sum occurs.

The tolerances occurring in the application (in particular tolerances with respect to the distance in the radial direction and with respect to a distance in the axial direction between the first sensor and the permanent magnet), which may occur during assembly of the sensor arrangement or when arranged in an actuator and the possibly can additionally vary during rotation of the permanent magnet, lead to larger errors in the measurement of the number of revolutions of the permanent magnet.

Due to the arrangement of the first sensor at a calculated distance from the rotation axis, the difference between the minimum vector sum and the maximum vector sum could be significantly reduced.

In particular, the sensor arrangement comprises a second sensor, which is arranged stationary relative to the rotatable permanent magnet, wherein the second sensor is a single-turn sensor which is suitable for determining an angular position within a single revolution of the permanent magnet.

Preferably, the first sensor and the second sensor detect differently aligned magnetic fluxes. The second sensor detects the exact angular position of the permanent magnet within one revolution and the first sensor the number of revolutions. Together, such a precise angular position or a position along an axial direction of an actuator can be provided.

In this case, only one permanent magnet is required for the sensor arrangement, whose magnetic field is detected by two sensors.

Preferably, the first and the second sensor in the axial direction, ie parallel to the axis of rotation, equally spaced from the permanent magnet, in particular in a common XY plane. It is further proposed an actuator, at least comprising a shaft having a rotation axis and a sensor arrangement according to the invention, wherein the permanent magnet is arranged coaxially to the shaft and rotatably connected to the shaft.

In particular, the actuator is a clutch actuator, wherein the actuator comprises a drive unit as a shaft and an actuating unit, wherein the actuating unit is displaceable by an rotation of the drive unit along an axial direction, wherein at least the number of revolutions of the drive unit and thus a position of the Actuator along the axial direction can be determined.

Preferably, the actuator comprises a planetary roller screw (PWG) as an actuating unit. Such an actuator with a Planetenwälzgewindespindel is z. B. from WO 2015/1 17612 A1, which is hereby incorporated by reference in its entirety in terms of the structure of the actuator proposed therein.

In particular, the actuator comprises an electric motor with a stator and a rotor, wherein the rotor forms the shaft.

In the case of the PWG, the rotor is rotatably connected to a sleeve of a planetary gear, which comprises the Planetenwälzgewindespindel, and supported in the sleeve planet carriers, so that a rotatably supported Planetenwälzgewindespindel upon rotation of the rotor and the sleeve supported in the planet carrier in the axial direction is. The Planetenwälzgewindespindel in this case forms the actuator of the actuator.

The invention and the technical environment will be explained in more detail with reference to FIGS. The figures show particularly preferred embodiments, to which the invention is not limited. In particular, it should be noted that the figures and in particular the illustrated proportions are only schematic. Like reference numerals designate like objects. Show it: 1 shows an actuator with a sensor arrangement in a side view in section;

2 shows a sensor arrangement in a plan view;

3 shows the sensor arrangement from FIG. 2 in a side view in section;

4 shows the sensor arrangement from FIGS. 2 and 3 in a further side view in FIG

Cut; and

5 shows the course of the magnetic flux density of the magnetic flux in the magnetic field directions over a distance from the axis of rotation.

1 shows an actuator 37 with a sensor arrangement 3 in a side view in section. A hollow cylindrical permanent magnet 1 is arranged coaxially to a rotation axis 8. A stationary relative to the rotatable permanent magnet 1 second sensor 50 is used to determine the angular position 3 of the permanent magnet. 1 The second sensor 50 is a single-turn sensor having a measuring range of 360 degrees. A single-turn sensor is a sensor that can not detect a number of revolutions 36, as it only resolves an angular range of 360 degrees (ie it detects an angular position within one revolution 36).

The second sensor 50 is arranged in a radial direction 35 at a distance from the axis of rotation 8. The second sensor 50 is thus not arranged on the axis of rotation 8 of the permanent magnet 1, but at a distance from the axis of rotation 8. The second sensor 50 is arranged in the axial direction 34, ie parallel to the axis of rotation 8, at a distance from the permanent magnet 1 ,

Furthermore, the sensor arrangement 3 comprises a first sensor 3 arranged stationary relative to the rotatable permanent magnet 1, the first sensor 33 being a multi-turn sensor suitable for determining a number of revolutions 36 of the permanent magnet 1. The first sensor 33 is in the axial direction 34, ie parallel to the axis of rotation 8, at a distance 19 from the permanent magnet 1 and in the radial direction 35 radially outward of the second sensor 50 and at a distance 20 from the axis of rotation 8. The first sensor 33 detects the magnetic field directions of the magnetic flux 27 in the radial magnetic field direction 30 and the tangential magnetic field direction 29 for determining the number of revolutions 36.

The second sensor 50 thus detects the exact angular position of the permanent magnet 1 within one revolution 36 and the first sensor 33 the number of revolutions 36. Together, a precise angular position or a position 42 along an axial direction 34 of an actuator 37 can be provided.

In this case, only one permanent magnet 1 is required for the sensor arrangement 2, whose magnetic field 26 is detected by two sensors 33, 50.

The actuator 37 comprises a shaft 38 with a rotation axis 8 and a sensor arrangement 2, wherein the permanent magnet 1 is arranged coaxially to the shaft 38 and rotatably connected to the shaft 38.

The actuator 37 is a clutch actuator, wherein the actuator 37 comprises a drive unit 39 as a shaft 38 and an actuator unit 40, wherein the actuator unit 40 by a rotation 41 of the drive unit 39 along the axial direction 34 is displaceable, wherein at least the number of revolutions of the drive unit 39 and thus a position 42 of the actuating unit 40 along the axial direction 34 can be determined.

Actuator 37 comprises a planetary roller screw spindle (PWG) 43 as actuating unit 40. Such an actuator 37 with a planetary roller screw 43 is known from WO 2015/1 17612 A1, which is hereby incorporated by reference in its entirety with respect to the construction of the actuator proposed therein. The actuator 37 comprises an electric motor 45 with a stator 46 and a rotor 47, wherein the rotor 47 forms the shaft 38. The rotor 47 is rotatably connected to a sleeve 48 of the Planetenwälzgewindespindel 43 comprehensive planetary gear 44, and supported in the sleeve 48 planet carriers 49 so that a rotatably supported Planetenwälzgewindespindel 43 upon rotation 41 of the rotor 47 and supported in the sleeve 48 Planet carrier 49 in the axial direction 34 is displaced. The Planetenwälzgewindespindel 43 forms the actuator unit 40 of the actuator 37th

2 shows a sensor arrangement 2 in a plan view along the axial direction 34. FIG. 3 shows the sensor arrangement 2 from FIG. 2 in a side view in section AA. FIGS. 2 and 3 will be described jointly below.

The sensor arrangement 2 comprises the first sensor 33 and the permanent magnet 1. The end faces 4, 5 of the permanent magnet 1 lie in an XY plane 6, and a central axis 7 extends transversely to the XY plane 6 and coaxially with a rotation axis 8 of the permanent magnet 1. The permanent magnet 1 has exactly two poles 9, 10, which are arranged in the XY plane 6 on opposite sides 1 1, 12 of the permanent magnet 1, so that the permanent magnet 1 is diametrically magnetized. A magnetic field 26 of the permanent magnet 1 has a magnetic flux 27 which can be represented at any position 28 in the magnetic field 26 by a vector. The vector comprises a tangential magnetic field direction 29, a radial magnetic field direction 30 and a normal (axial) magnetic field direction 31; the tangential magnetic field direction 29 being parallel to the XY plane 6 and parallel to the orientation 32 of the poles 9, 10; wherein the radial magnetic field direction 30 is parallel to the X-Y plane 6 and transverse to the orientation 32 of the poles 9, 10; wherein the normal magnetic field direction 31 extends transversely to the tangential magnetic field direction 29 and the radial magnetic field direction 30. A stationary relative to the rotatable permanent magnet 1 first sensor 33 detected to determine the number of revolutions 36 of the permanent magnet 1, the magnetic field directions 29, 30, 31 of the magnetic flux 27 in the tangential magnetic field direction 29 and the radial magnetic field direction 30th The permanent magnet 1 shown here is a hollow cylinder with an outer circumferential line 16 in circular form 18, ie with a diameter 25, and a central axis 7 which extends between two mutually parallel end faces 4, 5 along a rotation axis 8. The permanent magnet 1 is diametrically magnetized, that is, the two magnetic poles 9, 10 are respectively disposed on the outer peripheral surface 15, on opposite sides 1 1, 12 of the permanent magnet 1. The poles 9, 10 can be connected to each other by a straight line that intersects the central axis 8 of the permanent magnet 1 (see arrow for alignment 32).

The first sensor 33 is arranged in a radial direction 35 at a distance 20 from the axis of rotation 8 and from the permanent magnet or its outer circumferential surface 15. The first sensor 33 is thus not arranged on the axis of rotation 8 of the permanent magnet 1, but at a distance 20 from the axis of rotation 8. The first sensor 33 is in the axial direction 34, ie parallel to the axis of rotation 8, at a distance 19 from the permanent magnet 1 arranged.

The permanent magnet 1 shown here has coaxial with the central axis 7 an opening 13, wherein an inner peripheral surface 14 and an outer peripheral surface 15 each extend parallel to the central axis 7.

4 shows the sensor arrangement 2 from FIGS. 2 and 3 in a further side view in section. The distance 19 is determined between each other, along the axial direction 34, nearest points of the first sensor 33 and permanent magnet 1. Next, the permanent magnet 1 between the end faces 4, 5 has a thickness 53 of 3 to 6 mm. The distance 20 is determined between the axis of rotation 8 and a center of the first sensor 33 along the radial direction 35.

The tolerances occurring in the application (in particular tolerances with respect to the distance 20 in the radial direction 35 and with respect to a distance 19 in the axial direction 34 between the first sensor 33 and the permanent magnet 1), which can occur during assembly of the sensor arrangement 2 or when arranged in an actuator 37 and which may additionally vary when rotating the permanent magnet 1 (indicated here as shaded), lead to larger errors in the measurement of the number of revolutions of the permanent magnet. 1

As a result of the arrangement of the first sensor 33 at a calculated distance 20 from the axis of rotation 8 and the outer peripheral surface 15 of the permanent magnet 1, the difference between the minimum vector sum and the maximum vector sum could be significantly reduced. Furthermore, a smaller spread of the vector sum occurs.

5 shows the course of the magnetic flux density 51 of the magnetic flux 27 in the magnetic field directions 29, 30 over a distance 20 of the first sensor 33 from the axis of rotation 8. The wide curves for the radial flux density 21 and the tangential flux density 22 already take into account a possible Deviation of a distance 19 of +/- 0.5 mm (see shaded representation of the permanent magnet in Fig. 4).

In this area 54 by an (ideal) distance 20, the first sensor 33 is to be arranged opposite the axis of rotation 33 (see shaded representation of the first sensor 33 in FIG. 4).

Reference list permanent magnet

sensor arrangement

angular position

first end face

second end face

X-Y plane

central axis

axis of rotation

first pole

second pole

first page

second page

opening

Inner circumferential surface

Outer circumferential surface

Outer circumferential line

cross-section

circularity

distance

radial flux density

tangential flux density

first limit

second limit

diameter

magnetic field

magnetic river

position

tangential magnetic field direction radial magnetic field direction normal magnetic field direction alignment

first sensor

axial direction

radial direction

revolution

actuator

wave

drive unit

operating unit

rotation

position

Planetary roller screw planetary gear

electric motor

stator

rotor

shell

planet carrier

second sensor

magnetic flux density angle

thickness

Area

Claims

claims

1 . Sensor arrangement (2) for determining a number of revolutions (36) of a permanent magnet (1), wherein end faces (4, 5) of the permanent magnet (1) each lie in an XY plane (6) and a central axis (7) transversely to the XY plane (6) and coaxial with a rotation axis (8) of the permanent magnet (1); wherein the permanent magnet (1) has exactly two poles (9, 10) which are arranged in the XY plane (6) on opposite sides (11, 12) of the permanent magnet (1) such that the permanent magnet (1) is diametrically magnetized; wherein the permanent magnet (1) has an opening (13) coaxial with the central axis (7); wherein an inner peripheral surface (14) and an outer peripheral surface (15) each extend substantially parallel to the central axis (7); wherein a first sensor (33) fixedly arranged relative to the permanent magnet (1) rotatable about the rotation axis (8) in an axial direction (34), ie parallel to the axis of rotation (8), at a distance (19) from the permanent magnet (1 ) and in a radial direction (35) radially outside the outer peripheral surface (15) at a distance (20) from the rotation axis (8) is arranged; wherein the distance (20) is selected such that a vector sum of a radial flux density (21) and a tangential flux density (22) does not fall below a first limit value (23) and does not exceed a second limit value (24).

2. Sensor arrangement (2) according to claim 1, wherein a magnetic field (26) of the permanent magnet (1) has a magnetic flux (27), which at each position

(28) in the magnetic field (26) can be represented by a vector; the vector comprising a tangential magnetic field direction (29), a radial magnetic field direction (30) and a normal magnetic field direction (31); the tangential magnetic field direction (26) being parallel to the X-Y plane (6) and parallel to an orientation (32) of the poles (9, 10); the radial magnetic field direction (30) being parallel to the XY plane (6) and transverse to the orientation (32) of the poles (9, 10); the normal magnetic field direction (31) being transverse to the tangential magnetic field direction

(29) and the radial magnetic field direction (30); the first sensor (33) is a multi-turn sensor, which is suitable for determining a number of revolutions (36) of the permanent magnet (3), wherein the first sensor (33) for determining the number of revolutions (36), the magnetic field directions (29, 30) of the magnetic Flow (14) in the radial magnetic field direction (29) and the tangential magnetic field direction (30) detected.

3. Sensor arrangement (2) according to one of the preceding claims, wherein the first limit value (23) is 12 mT [MilliTesla] and the second limit value (24) is 37 mT.

4. Sensor arrangement (2) according to one of the preceding claims, wherein the distance (20) through

Distance = k ^* diameter outer peripheral surface + R ₀ ;

is determined; where k and R ₀ are dependent on at least the diameter

(25) of the outer peripheral surface (15) and the distance (19) are determined.

5. Sensor arrangement (2) according to claim 4, wherein at a distance (19) between 3 and 6 mm [millimeters] and a diameter (25) of the outer peripheral surface (15) between 18 and 30 mm for k and R ₀ :

k = 0.36 and

Ro = 7.45.

6. Sensor arrangement (2) according to any one of claims 4 or 5, wherein the permanent magnet (1) between the end faces (4, 5) has a thickness (53) of 3 to 6 mm.

7. Actuator (37), at least comprising a shaft (38) having a rotation axis (8) and a sensor arrangement (2) according to one of the preceding claims 1 to 6, wherein the permanent magnet (1) arranged coaxially with the shaft (38) and rotationally fixed is connected to the shaft (38).

8. actuator (37) according to claim 7, wherein the actuator (37) is a clutch actuator, wherein the actuator (37) comprises a drive unit (39) as a shaft (38) and an actuating unit (40), wherein the actuating unit (40). by a rotation (41) of the drive unit (39) along an axial direction (34) is displaceable, wherein by the sensor arrangement (2) at least the number of revolutions (36) of the drive unit (39) and thus a position (42) of the actuating unit (40) along the axial direction (34) can be determined.